An experimental demonstration on the recyclability of hybrid magnetite-humic acid nanoparticles

In this study, hybrid magnet-sensitive nanoparticles made by magnetite and humic acid are primarily obtained following a co-precipitation route. Subsequently, such hybrid systems are fully recycled following a two-step process, namely: (i) calcination under air (oxidizing) atmosphere, and (ii) acid digestion to obtain an Fe(III) aqueous solution. After neutralization, hybrid magnet-sensitive nanoparticles are re-synthesized following a properly modified synthetic route analogous to the previous one. Both hybrid nanoparticles are characterized by means of different morphological, structural, physicochemical, and magnetic techniques. Additionally, these magnet-sensitive hybrids are tested in the photocatalytic abatement of paracetamol from model wastewater, investigating a photo-Fenton degradation route. Experimental results evidence a superimposable degradation profiles of both hybrid nanoparticles, with an almost complete degradation of paracetamol after 120 min of UV irradiation (with 96–98 % of abatement). These results clearly demonstrate that the recycling route here proposed is an effective approach for the virtuous recycling of these hybrid nanoparticles, and the photocatalytic tests, although preliminary, encourage on the possibility of using these magnetic systems as substrates for the sustainable abatement of recalcitrant emerging micro-contaminants in wastewater treatments. • This study deals with the possibility of recycling hybrid magnetite nanoparticles starting from exhausted ones. • Hybrid nanoparticles are obtained following a co-precipitation method. • The proposed recycling route is a multi-step approach requiring calcination and acid treatment.